Conventional golf balls can be divided into two general types of groups: two piece balls or wound balls (also known as three piece balls). The difference in play characteristics resulting from these different types of construction can be quite significant.
Balls having a two piece construction are generally most popular with the average recreational golfer because they provide a very durable ball while also providing maximum distance. Two piece balls are made with a single solid core usually made of a cross linked rubber, which is enclosed by a cover material. Typically the solid core is made of polybutadiene which is chemically crosslinked with zinc diacrylate and/or similar crosslinking agents and is covered by a tough, cut-proof blended cover. The cover is generally a material such as SURLYN.RTM., which is a trademark for an ionomer resin produced by DuPont. The combination of the core and cover materials provide a "hard" ball that is virtually indestructible by golfers. Further, such a combination imparts a high initial velocity to the ball which results in improved distance. Because these materials are very rigid, two piece balls have a hard "feel" when struck with a club. Likewise, due to their hardness, these balls have a relatively low spin rate which provides greater distance.
At the present time, the wound ball remains the preferred ball of the more advanced player due to its spin and feel characteristics. Wound balls typically have either a solid rubber or liquid center core around which many yards of a stretched elastic thread are wound. The wound core is then covered with a durable cover material such as a SURLYN.RTM. or similar material or a softer cover such as Balata or polyurethane. Wound balls are generally softer and provide more spin, which enables a skilled golfer to have more control over the ball's flight and position. Particularly, with approach shots onto the green, the high spin rate of soft, wound balls enables the golfer to stop the ball very near its landing position.
Regardless of the form of the ball, players generally seek a golf ball that delivers maximum distance, which requires a high initial velocity upon impact. Therefore, in an effort to meet the demands of the marketplace, manufacturers strive to produce golf balls with initial velocities that approximate the maximum allowed by the USGA as closely as possible. Thus, golf ball manufacturers are continually searching for new ways in which to provide golf balls that deliver the maximum performance for golfers of all skill levels.
There are many prior art patents revealing balls with multi-layer constructions. However, in most of these patents each new layer is described as a uniquely spherical shell with an inner and outer radius from the center of the ball and uniform material properties within the layer. Thus, each layer is uniform in both its radius and in the materials with which it is constructed.
Other patents teach various constructions, however none teach the present invention. For example, U.S. Pat. Nos. 698,516 and 701,741 to Kempshall describe a golf ball formed with hemispherical plastic segments having indentations or perforations on their outer surface. A celluloid is spread over the surface and enters the indentations or perforations forming teeth or hobs all over the ball. A segment with an inner fabric is then placed over the ball and is compressed so that the celluloid becomes embedded in the fabric. This construction requires the use of additional materials including the fabric and the celluloid. Further, the ball is more difficult to construct.
U.S. Pat. No. 790,252 to Mahaut describes a construction of an intermediate layer made of a rubber composition with the outer surface formed of a succession of resilient projections in the form of knobs. The knobs however are compressed by the outer jacket of a smooth cylindrical shape. The advantage of a solid transition layer made of two adjacent layers is not realized.
U.S. Pat. No. 1,855,448 to Hazeltine discloses a golf ball having a mesh work placed over the core of the ball, and a cover is molded over the mesh work. This construction requires the use of additional materials including the mesh work.
U.S. Pat. No. 2,364,955 to Diddel discloses a golf ball having a core with cylindrical bores, a rod like material is placed within the bores and the ball is covered. This construction also uses additional materials, including the material placed in the bores and does not form the transition layer from two adjacent layers.
Therefore, it would be advantageous to provide a golf ball with at least one layer that was not uniform in radius and/or materials, which would allow three layers to be created with only two different materials and two different process steps. The present invention provides such a layer within a golf ball.